Scientists in the US have identified tiny natural bubbles containing the ACE2 protein (evACE2) in the blood of COVID-19 patients that can block infection from broad strains of the SARS-CoV-2 virus.

The evACE2 are lipid vesicles in nanoparticle size that express the ACE2 protein on cells. These bubbles act as decoys to lure the SARS-CoV-2 virus away from the ACE2 protein, which acts as a gateway for the virus to infect cells. The evACE2 can serve as a therapeutic to be developed for prevention and treatment for current and future strains of SARS-CoV-2 and subsequent coronaviruses, the researchers said. Once developed as a therapeutic product, evACE2 have the potential to benefit people as a biological treatment with minimal toxicities, they said.

The study, published in the journal Nature Communications on 20 January, is the first to show evACE2 are capable of fighting the new SARS-CoV-2 variants with an equal or better efficacy than blocking the original strain. The researchers found that evACE2 exist in human blood as a natural anti-viral response. The more severe the response, the higher the levels of evACE2 detected in the patient's blood. "Whenever a new mutant strain of SARS-CoV-2 surges, the original vaccine and therapeutic antibodies may lose power against Alpha, Beta, Delta and the most recent, Omicron," said the study co-senior author Huiping Liu, an associate professor at Northwestern University.

"However, the beauty of evACE2 is its superpower in blocking broad strains of coronaviruses, including current SARS-CoV-2 and even future SARS coronaviruses from infecting humans," Liu said.  The SARS-CoV-2 spike protein grabs evACE2 instead of cellular ACE2, preventing the virus from entering the cell, they said.

Once captured, the virus will either float harmlessly around or be cleared by a macrophage immune cell, no longer causing the infection, according to the researchers. "The key takeaway from this study is the identification of naturally occurring extracellular vesicles in the body that express the ACE2 receptor on their surface and serve as part of the normal adaptive defence against COVID-19-causing viruses," said study co-senior author Raghu Kalluri from the University of Texas.

"Building upon this, we've discovered a way to harness this natural defence as a new potential therapy against this devastating virus, Kalluri said. The researchers noted that the COVID-19 pandemic has been extended and challenged by a constantly changing SARS-CoV-2 virus.

One of the biggest challenges, they explained, is the moving target of pathogenic coronavirus that constantly evolves into new virus strains with mutations. The team has a pending patent on evACE2. Their goal is to collaborate with industry partners and develop evACE2 as a biological therapeutic product -- nasal spray or injection -- for the prevention and treatment of COVID-19. The researchers have formed a startup company, Exomira, to take this patent and develop evACE2 as a therapeutic.